This invention relates to a device for use in dentistry to anchor a superstructure to a tooth understructure.
It has long been known to insert screws into pre-drilled holes in tooth structures to provide anchors for artificial superstructures. Originally this was done with a length of threaded rod which was screwed by hand into a pre-drilled bore using a shaped grip at the end of the rod. Surplus projecting rod was then cut off.
UK patents 1347226 and 1347227 described the use of a threaded rod having a point of weakness between a threaded anchoring part and a gripping part. The rod is fully screwed into a pre-drilled bore and further screwing action then causes the gripping part to be severed from the anchoring part.
In 1347226 two points of weakness are provided to give different lengths of anchoring parts, and the gripping part has a shank adapted to fit into a special chuck attachment for a conventional dentist""s drill.
In 1347227, there is one point of weakness, an anchoring head is provided on the threaded part, and the gripping part has a shank adapted to fit into a hand tool comprising a knurled knob which can be gripped between the fingers.
UK patent 1482681 describes a threaded rod having an integral shank with a point of weakness therebetween. The shank is shaped to fit directly into a conventional dentists drill (i.e. without requiring a special chuck or adaptor).
U.S. Pat. No. 4,202,101 describes one or two part dental anchors with wings formed on their ends, and a shank with an axial blind bore in which the winged end is inserted, the other end of the shank being adapted for driving connection to a chuck of a dental drill.
U.S. Pat. No. 4,155,162 describes a two part dental anchor with an L-shaped free end, for engaging in notches in a longitudinal slot in a cylindrical body, giving alternative extensions of the anchor from the body as the parts of the anchor are used in turn; U.S. Pat. No. 4,053,982 is related to this, disclosing a one, two or three sectioned dental anchor also with an L-shaped free end for engaging in a single notch in a cylindrical coupling body.
GB 1528245 describes a dental hand wrench, with a handling end portion, a cylindrical body, and a threaded pin connected to the body by a wasted portion so that the pin can be separated from the body after being normally screwed into a substrate.
It is convenient to be able to use the dentists drill to screw the anchoring device into the tooth. However, the above mentioned prior art arrangements which have this feature necessitate some modification or manipulation of the drill. Thus, with the arrangement of GB 1347226 it is necessary to fit a special chuck to the drill. With the arrangement of GB 1482681, although a special chuck is not required it is necessary to remove the drill bit and fit the shank of the anchoring device in place of the drill bit.
An object of the present invention is to provide an anchoring device which can be used with a dentist""s drill in a particularly convenient manner.
According to one aspect of the invention therefore there is provided a dental anchoring device comprising a threaded anchoring part, a connecting part adapted for detachable drivable connection to a dentist""s drill, and at least one position of weakness between the anchoring part and the connecting part, characterised in that the connecting part is adapted to be connected to the drill with a drill bit in the drill.
With this arrangement, conveniently the anchoring device can be connected to the drill after the drill has been used with a drill bit to drill a bore for the anchoring device in a tooth, without need for the drill bit to be removed. The threaded anchoring part can then be driven into the pre-drilled bore using the drill. Once the anchoring part is fully inserted the connecting part can be removed in conventional manner by severing at the position of weakness caused by further rotation of the connecting part by the drill. The severed connecting part can then be removed from the drill and discarded leaving the drill bit ready for further use.
With regard to the threaded part this may be a threaded metal rod which may be generally of conventional form. The position of weakness may be a waisted or cut away portion between the threaded rod and the adjacent portion of the connecting part. The rod, the waisted or cut-away portion and the adjacent portion may be formed in one piece.
According to a second aspect of the invention, there is provided a dental anchoring device comprising a threaded anchoring part, and a connecting part adapted for detachable driving connection to a dentist""s drill, the connecting part being drivably interconnected to the anchoring part so as to be releasable therefrom when a predetermined level of driving torque is exceeded characterised in that the connecting part is interconnected with the anchoring part by a structure which is adapted to rupture or deform circumferentially to permit said release thereof when said level of driving torque is exceeded.
Preferably said connecting part is adapted to be connected to the drill with a drill bit in the drill in accordance with the first aspect of the invention.
With regard to the rupturable or deformable structure, preferably this is achieved by drivable interconnection between relatively strong and weak parts, particularly between metal and plastics parts, so that the weaker part preferentially ruptures or deforms. Alternatively or additionally the drivable interconnection may be achieved between parts which are bonded or welded or similarly fixed together so that the bond or weld or other joint is preferentially ruptured.
In a particularly preferred embodiment the threaded anchoring part comprises a rod which is threaded at one end, and the connecting part comprises a plastics body which is moulded around the other end of the rod. The said other end of the rod may be appropriately configured, e.g. by provision of one or more xe2x80x98flatsxe2x80x99, to drivably key the rod circumferentially to the plastics body.
With the first aspect of the invention, and the second aspect when combined with the first aspect, the connecting part may have a receptacle in a body thereof to receive the drill bit. This may comprise an axial bore or the like whereby the body is generally of tubular construction having solid or open-work side walls. This body may be formed integrally in One piece with the above mentioned adjacent portion or may be a separate part fixed thereto (and may be formed from metal or plastics).
For detachable drivable connection relative to the drill the connecting part may incorporate a circumferential locking structure which incorporates elements to prevent rotation relative to the drill and/or a longitudinal locking structure which incorporates elements to restrict longitudinal separation from the drill.
Thus, the connecting part may have side abutment faces or the like which engage corresponding side abutment faces of the drill bit to prevent relative rotation. Conveniently, the former flat faces may be provided in the above mentioned axial bore.
The connecting part may have a deflectable abutment structure which makes a releasable snap fit to restrain longitudinal movement relative to the drill.
With reference to the connection between the anchoring device and the drill it is to be understood that this may take place directly, i.e. by interengagement between the anchoring device and the drill chuck, or indirectly i.e. by interengagement between the anchoring device and the drill bit as more particularly described above. Most preferably the latter arrangement is adopted and the interengagement is preferably effected with a shank part of the drill bit. Whatever drive connection is adopted this should most preferably be such as to permit ready attachment to give positive drive interconnection, and also to permit ready release so that, after use, the device can be conveniently removed to free the drill, and the drill bit for use.
With regard to the drill, this may be any suitable powered dentist""s drill or hand tool; and the bit may be any suitable kind of drill bit of twist or other form.